1. Field of the Invention
The present invention relates to an image processing system and a camera system, and particularly to an image processing system which compresses an image, transmits it, and expands it, and a camera system which compresses a picked up image and transmits it.
2. Description of the Related Art
In the case where a system with band limitation, for example, a USB (Universal Serial Bus) used for a personal computer or the like is considered as a transmission path of an image, according to the standard specification of the USB, the maximum transfer rate in the case where operation is made at full speed (12 MHz) and isochronous transfer is used, is 1.023 Mbyte/sec (=1,023 bytesxc3x971,000 frames/sec).
On the other hand, in the case where a normal CIF (Common Intermediate Format) size (358 horizontal pixelsxc3x97288 vertical pixels) is transferred in conformity with YUV of 4:2:2 at a frame rate of 30 fps (frame per second), a transfer width of 6.19 Mbyte/sec is necessary, and even in the case where YUV of 4:2:0 is adopted, a transfer width becomes 4.64 Mbyte/sec. Thus, it is necessary to make transmission after the image is compressed to at least about xc2xc.
In such an image processing system that an original image exists, compression processing is made to the image, transmission is made, and then, the compressed image is expanded so that the original image is restored, it is important that the difference between the image before the compression processing and the image after the expansion processing is small. Thus, conventionally, compression/expansion processing has been made by using DCT (Discrete Cosine Transform) coding, sub-band coding, wavelet coding, or the like.
On the other hand, in the case of an image processing system in which an image picked up by an image pickup device typified by a CCD (Charge Coupled Device) image sensor is compressed and transmitted, and this is expanded and is shown on, for example, a display of a personal computer, it is not necessary to show the image before the compression processing, and it is not necessary to cause the final image after the expansion processing to approach the state before the compression. That is, if the image after the expansion processing is adequate in picture quality, there is no problem.
Thus, with respect to the signal processing before the compression, it is satisfactory if optimum processing is carried out with a view to the compression. To such an image processing system, if a compression/expansion technique used for the foregoing image processing system in which the picture quality of an image before compression processing is required to be adequate and the picture quality after expansion processing is also required to be the same, is directly applied, there is a lot of waste and a circuit scale becomes large, so that the cost of the system is raised.
The present invention has been made in view of the above problem, and an object of the invention is to provide an image processing system and a camera system in each of which a circuit scale can be reduced and a lower cost system can be realized.
An image processing system of the present invention comprises coding means for dividing an output signal of an image pickup device with a color filter into a luminance signal and a contour correcting signal and for separately compressing and outputting these signals, a transmission path with band limitation for transmitting the luminance signal and the contour correcting signal compressed by the coding means, and decoding means for separately expanding the luminance signal and the contour correcting signal transmitted through the transmission path and for adding and outputting these signals.
In the image processing system of the above structure, the coding means uses a signal in a process of carrying out signal processing of the output signal of the image pickup device to divide the output signal into the luminance signal and the contour correcting signal, and separately compresses them. The compressed luminance signal and contour correcting signal are transmitted through the transmission path with band limitation. The decoding means separately expands the luminance signal and the contour correcting signal transmitted through the transmission path, and then, adds and outputs them.
A camera system of the present invention comprises an image pickup device with a color filter, an optical system for taking in incident light from an object and for causing imaging on an image pickup surface of the image pickup device, and coding means for dividing an output signal of the image pickup device into a luminance signal and a contour correcting signal and for separately compressing and outputting these signals.
In the camera system of the above structure, the image pickup device carries out photoelectric conversion in a pixel unit on the basis of image light of the object taken in by the optical system, and outputs pixel information as an image pickup signal. Receiving the image pickup signal, the coding means uses a signal in a process of carrying out signal processing to divide the image pickup signal into the luminance signal and the contour correcting signal, and separately compresses and outputs them.